Control group continuing the ongoing therapy STI group performing long term CD4 guided structured treatment interruptions In the STI arm patients will stay off therapy until their CD4 count will drop < 400 cells/mcL. At that time point patients will resume the HAART regimen they were assuming before STI and will continue HAART until they CD4 count will raise > 800 cells/mcL and their HIV-RNA will drop below the detection limit of 50 copies/ml. When both the CD4 count and the viral load will be within these pre-set values they will stop therapy again. There is no limit to the number of interruptions and re-start cycles during the study period The study is powered to evaluate equivalence between the two strategies under the assumption of a failure proportion in the control arm at each time point not greater than 5% and a maximum allowed difference of 15%.